Major, trace, and rare earth elements geochemistry and enrichment in the Neogene organic-rich sediments from the Aleksinac deposit (Serbia): Part A

Rare earth elements geochemistry in surface floodplain sediments from the Xiangjiang River, middle reach of Changjiang River, China

Rare earth and trace element geochemistry of termite mounds in central and northeastern Namibia: Mechanisms for micro-nutrient accumulation

This study focuses on the trace and rare earth elements (REE) geochemistry of the Nkporo and Ekenkpon Shales of the Calabar Flank. The main aim is to infer their depositional environment and the degree of their metal enrichment. The shale samples were analyzed using inductively coupled plasma mass spectrometry. The results indicated that the mean concentrations of K, Na, and Fe in Nkporo and Ekenkpon Shales are 1.45, 0.4, and 4.17 wt%, and 1.11, 0.44, and 5.42 wt%; respectively. The Nkporo Shale is enriched with the following trace elements; P > Mn > Sr > Ba > Zn > Ce > Rb > Zr > V>Cr > Ni and depleted in the following trace elements; Ta > Ge > Sb > Bi > Cd > Ag > Te > In > Hg. While the Ekenkpon Shale is enriched with the following trace elements; P > Mn > Ba > Sr > V>Ce > Zr > Rb > Cr > Zn > Ni and depleted in; Sb > Ge > Bi > Ag > Ce > Te > In > Hg. The concentration of redox-sensitive elements such as V, Ni, Mo, U, Cu, Cr, Re, Cd, Sb, Ti, Mn, and their ratio V/Mo and U/Mo in the black and grey shale samples show different patterns. The REE obtained from the Nkporo and Ekenkpon Shales were PAAS normalized. The Nkporo Shale showed a slightly flat light rare-earth element (LREE), middle rare-earth element (MREE), and heavy rare earth element (HREE) pattern enrichment. Ce/Ce* ranges from 0.95 to 1.09 in Nkporo Shale and 0.67 to 1.40 in Ekenkpon Shale. The Ekenkpon Shale showed a slight LREE, MREE enrichment, and depleted HREE patterns. The Mn contents and U/Mo ratio in Nkporo and Ekenkpon Shales suggests a poor oxygen transitional environment. The V/Mo and V/(V + Ni) ratios indicated that the Nkporo shales were deposited in an anoxic to suboxic conditions and Ekenkpon shales were also deposited under an anoxic to suboxic conditions. The V/Ni ratio indicated that the organic matter in the Nkporo shale is terrigenous while that of the Ekenkpon shales are both terrigenous and marine in origin.

Mineralogy, geochemistry and provenance of geophagic soils from Swaziland

Rare earth and major element geochemistry of Eocene fine-grained sediments in oil shale- and coal-bearing layers of the Meihe Basin, Northeast China

The concentration of trace and rare earth elements in 22 crude oil and five oilfield water samples, collected from Triassic Yanchang Formation and Jurassic Yanan Formation reservoirs in the Jiyuan Area of Ordos Basin, N China, was determined using inductively coupled plasma mass spectrometry (ICP‐MS) for the first time. The oil samples were analysed to classify the oils into family and to determine the origin and depositional environment of organic matter that yield the oils using trace elements. The REE chondrite‐normalized distribution patterns of the crude oils show light rare earth element (LREE) enrichment and right‐oblique curves. These patterns could be divided into two distinct types that were consistent with that of the upper continental crust (UCC) and lower continental crust (LCC) characterizing by negative Eu anomalies and positive Eu anomalies, respectively. The REE concentrations in coexisting water samples are less than those in crude oils by a factor of ten. Cluster analysis also classified the oil samples from the Ordos Basin into two main groups. Integrated analysis of Co/Ni, V/Ni and V/ (V + Ni) values suggests that the organic matter have more terrigenous source input and the palaeoenvironment was anoxic and slightly oxic conditions. This study differs from previous studies by using trace element analyses of crude oils to constrain oil‐source rock correlation. The results show that most of the crude oils in north Jiyuan area were derived from Chang 7 mudstones while those from Hongde area may be contributed by Chang 7 oil shales. Copyright © 2017 John Wiley & Sons, Ltd.

In the Tanshan area, in the Liupanshui Basin, abundant oil shale resources are associated with coals. We analyzed the cores, geochemistry of rare earth elements (REE), and trace element of oil shale with inductively coupled plasma mass spectrometry technology to define the paleo-sedimentary environment, material source, and geologic significance of oil shale in this area. The results of the summed compositions of REE, and the total REE contents (ΣREE), in the Yan’an Formation oil shale are slightly higher than the global average of the composition of the upper continental crustal and are lower than those of North American shales. The REE distribution pattern is characterized by right-inclined enrichment of light REEs (LREE) and relative loss of heavy REEs (HREE), which reflects the characteristics of crustal source deposition. There is a moderate degree of differentiation among LREE, whereas the differences among HREE are not obvious. The [Formula: see text] values indicate a weak negative anomaly, and the [Formula: see text] values indicate no anomaly, which are generally consistent with the distribution of REE in the upper crust. The characteristics of REE and trace elements indicate that the oil shale formed in an oxygen-poor reducing environment and that the paleoclimatic conditions were relatively warm and humid. The degree of differentiation of REE indicates that the sedimentation rate in the study area was low, which reflected the characteristics of relatively deep sedimentary water bodies and distant source areas. The results also proved that the source rock mainly consisted of calcareous mudstone, and a small amount of granite was also mixed in.

The Upper Devonian Shetianqiao Formation mudstones are considered to be the most petroliferous shale gas source rocks in the Shaoyang Sag of Xiangzhong Depression in China. These Shetianqiao dark mudstones have been collected systematically to investigate their geochemical characteristics by analysing their major elements, trace elements, and rare earth elements (REEs), in order to reveal their provenance, palaeoenvironment and tectonic setting. The results show that the total REEs content (ΣREE) of dark mudstone is 34.22–246.62 ppm (average 131.66 ppm) and characterized by low ΣREE, light rare earth element (LREE) enrichments, negative Eu anomalies, and minor negative Ce anomalies. The normalized distribution pattern of REE, Eu anomaly, as well as discrimination diagrams of trace elements and REEs, are applied to explain the source rock types and properties of Shetianqiao mudstones. The results indicate that the sediments have a weak sedimentary recycling and mainly originated from the upper continental crust, and the source rocks of the black mudstones are mainly constituted by felsic granite. The Ce anomaly, Th/U, V/Sc, V/Cr, and V/(Ni + V) ratios of the dark mudstones suggest a long‐term oxidizing depositional environment interrupted by a short period of a dysoxic/anoxic depositional environment in the middle section of the formation. This short period corresponds to a dramatic marine transgression with relatively high TOC. The La/Ce, LaN/SmN, Ce anomaly, and normalized REE distribution pattern characteristics indicate that the depositional process of the Shetianqiao mudstones has consistently been influenced by the regional upwelling hydrothermal activities. The chemical index of alteration (CIA) and Al2O3‐(CaO* + Na2O)‐K2O triangular plot reveal that a warm and humid climate with moderate chemical weathering in the source areas of the Shetianqiao mudstones occurred during the deposition. The ratio of major elements, trace elements, and REEs are used to analyse the tectonic setting of the depositional area which suggests that the source area is dominated by continental island arc tectonic setting. Combined with the previous regional studies, it is concluded that the continental island arc granite formed by plate collisions in the Caledonian stage constitutes the main source of the Shaoyang Sag during the Shetianqiao period. The depositional environment was not stable due to the lasting influence of deep hydrothermal activities. The upwelling currents controlled by hydrothermal activity transport nutrients to the study area, resulting in the formation of organic‐rich mudstones.

BackgroundRare earth elements (REE) are a group of trace elements that behave geochemically coherently. REE fractionation patterns normalized to reference materials provide a powerful tool for documenting pedogenesis. In-soil processes are particularly difficult to illustrate with respect to contemporary and past climate conditions. In this study, we characterize the rare earth element (REE) contents in bulk soils and respective geochemical fractions (e.g., exchangeable, carbonate-bound, reducible, and oxidizable fractions) and to decipher the relationships between REE geochemistry components and climatic factors across a large-scale northern China transect (NCT).ResultsAcross the NCT, bulk REE concentrations ranged from 55.2 to 241.1 μg g−1 with a main portion in the residual fraction (49–79%), followed by oxidizable fraction (2–40%), reducible fraction (3–22%), carbonate-bound fraction (0.1–16%), and negligible exchangeable fraction. The REE contents of geochemical components (carbonate-bound, reducible, and oxidizable) in topsoils correlated to climate factors (mean annual precipitation, mean annual temperature, potential evaporation, and aridity index (AI)). The normalized abundances to the upper continental crust (UCC) composition show that the middle REE was generally enriched than the light REE and heavy REE in topsoils along the transect. The overall UCC-normalized bulk REE patterns in topsoils and subsoils were similar, characterized by weak negative Ce anomalies and positive Eu anomalies.ConclusionsOur data in topsoils and depth profiles collectively suggest that cycling of REE was primarily regulated by abiotic processes in area with AI < 0.2, while the biological effect on REE circulation in soil played a more effective role in area with AI > 0.3. The similar UCC normalized patterns in topsoils suggest that the REE was originated from a common source with limited influences from other sources (e.g., atmospheric dusts and anthropogenic contributions). Our results to some extent provide evidence for climatic influence REE distribution patterns both in topsoils and subsoils across the continental-scale transect. Our investigation gives insights into future studies on vertical REE mobility and its associated biogeochemical pathways.

통가열도 내 우리나라 해저열수광상 독점 탐사지역에 위치하는 5개 해저화산(TA12, TA19, TA22, TA25, TA26) 주변 표층 퇴적물의 열수변질 여부를 규명하고, 열수변질 특성을 확인하기 위하여 각 해저화산에서 채취된 29개의 표층 퇴적물에 대해 미량 원소와 희토류 원소 분석을 실시하였다. 분석 결과 TA12, TA19, TA22 해저화산에서는 열수에 의한 퇴적물의 변질작용이 없거나 매우 적은 것으로 나타났으며, TA25와 TA26 해저화산의 일부 지역은 현재에도 열수의 영향을 받고 있는 것으로 나타났다. 열수의 영향이 있는 해저화산 사이에도 부화된 미량 원소의 종류에 차이가 있는데, TA25 해저화산의 경우 주로 Ni, Cu, Sn, Zn, Pb, Cr, Cd, Sb, W, Ba, Ta, Rb, Sr, As가, TA26 해저화산에서는 주로 Cu, Sn, Zn, Pb, Cd, Sb, Ba, Rb, Sr이 부화되어 있다. 미량 원소의 부화가 확인된 지역은 희토류 원소의 부화도 관찰된다. 상부지각 희토류 원소 농도로 표준화된 희토류 원소의 분포형태는 가벼운 희토류 원소(LREE)가 매우 낮고 중간 희토류 원소(MREE)에서 무거운 희토류 원소(HREE)로 갈수록 증가하는 형태를 보이며, TA25와 TA26 해저화산의 일부 정점에서 Eu의 부화가 확인된다. 또한 TA26 해저화산의 일부 정점에서 Ce이 부화가 관찰되었는데, 이는 주변지역에서 채취된 열수 내 희토류 원소의 높은 Ce분포형태와 매우 유사하다. 또한 TA25와 TA26 해저화산은 부화된 원소의 특징이 다르게 나타나는데, TA25 해저화산에서는 Cu를 포함한 미량 원소가, TA26 해저화산에서는 Ce와 Eu를 포함한 희토류 원소가 우세하게 부화되어 있는 것으로 나타났다. 조사결과 나타난 각 해저화산 표층 퇴적물 내 부화된 미량 원소 및 희토류 원소의 종류와 농도는 차후 통가열도 지역의 열수광상 탐사시에 지역적인 열수변질의 지시자로써 유용하게 활용될 것으로 판단된다. We analyzed 29 surface sediment samples in five submarine volcanoes (TA12, TA19, TA22, TA25, and TA26) located in the southern part of the Tonga arc for trace elements and rare earth elements to investigate characteristics of the hydrothermal alteration of surface sediments. Based on analytical results of trace element and rare earth element (REE), surface sediments of TA12, TA19, and TA22 submarine volcanoes, which are located in the northern part of the study area, were very little or not influenced by hydrothermal fluids. In contrast, some stations of TA25 and TA26 submarine volcanoes were strongly affected by hydrothermal fluids. However, these two submarine volcanoes showed different features in element concentration in the sediments. Some stations of TA25 submarine volcano showed enrichment of Ni, Cu, Sn, Zn, Pb, Cr, Cd, Sb, W, Ba, Ta, Rb, Sr, and As, however, those of TA26 submarine volcano showed enrichment of Sn, Zn, Pb, Cd, Sb, Ba, Rb, and Sr. Stations which enriched trace elements were observed, enriched REEs were also observed. Average upper continental crust (UCC)-normalized REE patterns of the surface sediments generally showed low light REE (LREE) abundances and increased heavy REE (HREE) abundances. Eu enrichment was identified at several stations of TA25 and TA26 submarine volcanoes. In addition, enrichment of Ce was found at some stations of TA26 submarine volcano and these enrichment patterns were similar with hydrothermal fluid of near stations. Furthermore, TA25 and TA26 submarine volcanoes showed different enrichment characteristics of trace elements and REE. Trace elements were concentrated at TA25 submarine volcano. TA26 submarine volcano, on the other hand, observed highly enrichment of REE especially, Eu and Ce. As a result of the investigation, the characteristics and concentrations of REEs and trace elements in the surface sediments of each submarine volcano can be applied to identify hydrothermal alteration of sediments during exploration for hydrothermal deposits.

Chemical environment of cold seep carbonate formation on the northern continental slope of South China Sea: Evidence from trace and rare earth element geochemistry

Instrumental neutron activation analysis was used to determine nine rare earth elements (REE), Sc and five high field‐strength elements (HFSE) in the Multani Mitti (MM) clay. Chondrite‐normalised rare earth element patterns for the MM clay compared with those for the Post‐Archaean Australian Shale (PAAS), Upper Continental Crust (UCC) and North American Shale Composite (NASC) showed enrichment of light REEs and depletion of heavy REEs with a slight negative Eu anomaly. The Multani Mitti clay showed close resemblance to PAAS and NASC in its average REE and HFSE contents. Positive correlations between La/Ce, La/Sm, La/Yb, Zr/Hf, Th/U and Th/Ta ratios predict enrichment of LREEs, Zr and Th and depletion of HREEs. A parent source of felsic origin for the MM clay is also endorsed through the high La/Th and low Th/Sc ratios observed.

Geochemistry of trace and rare earth elements during weathering of black shale profiles in Northeast Chongqing, Southwestern China: Their mobilization, redistribution, and fractionation

The major, trace and rare earth element (REE) composition of Late Archean manganese, ferromanganese and iron ores from the Iron Ore Group (IOG) in Orissa, east India, was examined. Manganese deposits, occurring above the iron formations of the IOG, display massive, rhythmically laminated or botryoidal textures. The ores are composed primarily of iron and manganese, and are low in other major and trace elements such as SiO2, Al2O3, P2O5and Zr. The total REE concentration is as high as 975 ppm in manganese ores, whereas concentrations as high as 345 ppm and 211 ppm are found in ferromanganese and iron ores, respectively. Heavy REE (HREE) enrichments, negative Ce anomalies and positive Eu anomalies were observed in post‐Archean average shale (PAAS)‐normalized REE patterns of the IOG manganese and ferromanganese ores. The stratiform or stratabound shapes of ore bodies within the shale horizon, and REE geochemistry, suggest that the manganese and ferromanganese ores of the IOG were formed by iron and/or manganese precipitation from a submarine, hydrothermal solution under oxic conditions that occurred as a result of mixing with oxic seawater. While HREE concentrations in the Late Archean manganese and ferromanganese ores in the IOG are slightly less than those of the Phanerozoic ferromanganese ores in Japan, HREE resources in the IOG manganese deposits appear to be two orders of magnitude higher because of the large size of the deposits. Although a reliable, economic concentration technique for HREE from manganese and ferromanganese ores has not yet been developed, those ores could be an important future source of HREE.

Inatlar limestone, which is dated to the Middle Jurassic–Lower Cretaceous, is exposed between the villages of Kabulbaba and Söğütalan in the Mustafakemalpaşa district of Bursa, Turkey. This study investigates its mineralogical, petrographic, and geochemical characteristics, focusing on major, trace, and rare earth element (REEs) compositions to interpret the depositional environment, paleoenvironmental conditions, and diagenetic processes. Petrographic analysis identified four main limestone types: siliceous, micritic, fossiliferous, and dolomitic. REEs geochemistry indicates enrichment in heavy REEs (HREEs), depletion in light REEs (LREEs), and characteristic anomalies with negative Ce and Eu and positive La, suggesting an open marine depositional environment and early diagenesis. Trace element data point to deposition in settings ranging from continental margins to open marine environments. Ni and V concentrations reflect a spectrum of depositional conditions, including terrestrial, transitional (oxic–dysoxic), and marine anoxic settings. Z values support the theory that the limestones have a marine origin. δ13C and δ18O isotope values indicate deposition in both hydrothermal and typical marine carbonate environments. Y/Ho and Er/Nd ratios reveal the influence of terrestrial input, as well as diagenetic and detrital material. Furthermore, V/(V + Ni) ratios reflect fluctuating oxic to suboxic/anoxic conditions, while Ni/Co ratios indicate predominantly euxinic and, to a lesser extent, anoxic conditions. Altogether, these geochemical signatures suggest that the Inatlar limestone was deposited in a dynamic marine system characterized by variable redox states and salinity fluctuations.